I agree it was a mistake, but in Reagan’s defense, he had a front row seat to how Eisenhower and the Establishment went against Goldwater in 64, and thought he needed to unite the party in 1980 to win.
“he had a front row seat to how Eisenhower and the Establishment went against Goldwater in 64”
Eisenhower supported Goldwater in the 1964 election.
Nelson Rockefeller and other prominent Republicans didn’t. Some openly backed LBJ.